The outgoing trusts page for the organization shows the list of outgoing trusts that have been configured:

Important: Before you can create an outgoing trust, you need the App Store ID of the organization that you want to trust. You can contact the organization directly to request this ID from them. To request your own organization ID, please contact Intelligent Plant.

To create an outgoing trust, click on the Add Trust button. This will display the outgoing trust editor:

Enter the ID of the organization you want to trust. You can optionally provide an expiry date for the trust. Click Create Trust to save the changes. The new trust will be added to the list:

Please note that the 3rd party organization can choose whether or not to accept your trust request, and can apply its own expiry trust expiry date, which is not visible to your organization.